It is known that a polysaccharide having an anti-tumour activity can be obtained by refining the extract of a Basidiomycetes with an aqueous solvent. Such method, however, has a serious drawback that the extraction efficiency of the active component is low, resulting in sizable loss of the valuable anti-tumour substance, and hence such method has little practical utility, particularly from the viewpoint of adaptability to industrial production of an anti-tumour substance from the fungus.